Concat scripts in order with Gulp

Say, for example, you are building a project on Backbone or whatever and you need to load scripts in a certain order, e.g. underscore.js needs to be loaded before backbone.js.

How do I get it to concat the scripts so that they’re in order?

// JS concat, strip debugging and minify
gulp.task('scripts', function() {
    gulp.src(['./source/js/*.js', './source/js/**/*.js'])
    .pipe(concat('script.js'))
    .pipe(stripDebug())
    .pipe(uglify())
    .pipe(gulp.dest('./build/js/'));
});

I have the right order of scripts in my source/index.html, but since files are organized by alphabetic order, gulp will concat underscore.js after backbone.js, and the order of the scripts in my source/index.html does not matter, it looks at the files in the directory.

So does anyone have an idea on this?

Best idea I have is to rename the vendor scripts with 1, 2, 3 to give them the proper order, but I am not sure if I like this.

As I learned more I found Browserify is a great solution, it can be a pain at first but it’s great.

I had a similar problem recently with Grunt when building my AngularJS app. Here's a question I posted.

What I ended up doing is to explicitly list the files in order in the grunt config. The config file will then look like this:

[
  '/path/to/app.js',
  '/path/to/mymodule/mymodule.js',
  '/path/to/mymodule/mymodule/*.js'
]

Grunt is able to figure out which files are duplicates and not include them. The same technique will work with Gulp as well.

Another thing that helps if you need some files to come after a blob of files, is to exclude specific files from your glob, like so:

[
  '/src/**/!(foobar)*.js', // all files that end in .js EXCEPT foobar*.js
  '/src/js/foobar.js',
]

You can combine this with specifying files that need to come first as explained in Chad Johnson's answer.

I have used the gulp-order plugin but it is not always successful as you can see by my stack overflow post gulp-order node module with merged streams. When browsing through the Gulp docs I came across the streamque module which has worked quite well for specifying order of in my case concatenation. https://github.com/gulpjs/gulp/blob/master/docs/recipes/using-multiple-sources-in-one-task.md

Example of how I used it is below

var gulp         = require('gulp');
var concat       = require('gulp-concat');
var handleErrors = require('../util/handleErrors');
var streamqueue  = require('streamqueue');

gulp.task('scripts', function() {
    return streamqueue({ objectMode: true },
        gulp.src('./public/angular/config/*.js'),
        gulp.src('./public/angular/services/**/*.js'),
        gulp.src('./public/angular/modules/**/*.js'),
        gulp.src('./public/angular/primitives/**/*.js'),
        gulp.src('./public/js/**/*.js')
    )
        .pipe(concat('app.js'))
        .pipe(gulp.dest('./public/build/js'))
        .on('error', handleErrors);
});

With gulp-useref you can concatenate every script declared in your index file, in the order in which you declare it.

https://www.npmjs.com/package/gulp-useref

var $ = require('gulp-load-plugins')();
gulp.task('jsbuild', function () {
  var assets = $.useref.assets({searchPath: '{.tmp,app}'});
  return gulp.src('app/**/*.html')
    .pipe(assets)
    .pipe($.if('*.js', $.uglify({preserveComments: 'some'})))
    .pipe(gulp.dest('dist'))
    .pipe($.size({title: 'html'}));
});

And in the HTML you have to declare the name of the build file you want to generate, like this:

<!-- build:js js/main.min.js -->
    <script src="js/vendor/vendor.js"></script>
    <script src="js/modules/test.js"></script>
    <script src="js/main.js"></script>

In your build directory you will have the reference to main.min.js which will contain vendor.js, test.js, and main.js

The sort-stream may also be used to ensure specific order of files with gulp.src. Sample code that puts the backbone.js always as the last file to process:

var gulp = require('gulp');
var sort = require('sort-stream');
gulp.task('scripts', function() {
gulp.src(['./source/js/*.js', './source/js/**/*.js'])
  .pipe(sort(function(a, b){
    aScore = a.path.match(/backbone.js$/) ? 1 : 0;
    bScore = b.path.match(/backbone.js$/) ? 1 : 0;
    return aScore - bScore;
  }))
  .pipe(concat('script.js'))
  .pipe(stripDebug())
  .pipe(uglify())
  .pipe(gulp.dest('./build/js/'));
});